Along the per-gear ignition compensation mentioned here, the boost control system on the new turbo’d Subarus can also be linked to the gear currently in use.Â The Throttle-by-Wire system converts the pedal position to a number called Requested Torque.Â This Requested Torque value is then used to look up a desired boost target.
Since boost target is not directly linked to the pedal position, it can be manipulated by altering the Requested Torque value. The ECU can limit Requested Torque to a value based on which gear it is in. For example, if I set the maximum Requested Torque value to 400 (even though the throttle table calls for 428), it would limit the boost target to those values in the second-to-last column. At 3200 rpm, the target would be lowered from 19.9 to 19psi.
In the example below, boost target was lowered in 5th gear, to reduce stress on the engine at full throttle. Red traces indicate boost target (accounting for elevation and temperature)